We plan to investigate the functional relations between motor cortex cells and forelimb nuscles in macaque monkeys trained to perform appropriate wrist movements. Effects of single cortical cells on forearm activity will be documented by compiling spike-triggered averages of rectified EMG activity of 12 implanted flexors and extensors of wrist and digits. Corticomotoneuronal (CM) cells, which facilitate muscle activity, will be studied during different types of motor responses to determine (a) their affects on identified motor units within facilitated muscles, (b) their effects on antagonists of their target muscles and (c) the degree to which their activity can be dissociated from target muscle activity by operant conditioning techniques. Functional connection of CM cells to cervical motoneurons will be further investigated by recording intracellularly the post-synaptic potentials which CM cells evoke in identified forelimb motoneurons. The location in cervical spinal cord of motoneuron pools of important forelimb muscles will be mapped by retrograde transport of horseradish peroxidase. These studies will further elucidate the functional organization of the primate corticomotoneuronal system.